Subsea oil and gas field architecture integrates a pipeline network to transport the production fluid from the wellhead to the surface facilities. As part of this pipeline network a riser pipe structure is provided close to the surface process facilities to lift the fluid from the seabed to the surface.
The riser structure may contain a buoyancy tank providing an uplift tension to one or more vertical riser pipe(s) and a flexible pipe connecting the top of the vertical riser to surface process facilities.
Accidental flooding of the buoyancy tank could create a potential hazard to the riser structure and expose the field to a risk of catastrophic failure if a sufficient uplift tension is not applied to the vertical riser pipe system. In order to mitigate this risk, operators may request to install instrumentation to monitor possible accidental flooding of the buoyancy tank. To this end, the tension generated by the buoyancy is permanently monitored by means of an integrity monitoring system sensor equipped with gages able to measure the pipe strain. Such a system is acceptable for monitoring sudden event but could be limited in case of slow water intrusion inside the tank due, for instance, to corrosion.